CIRCUIT
15
3-5. N
ORMAL
A
UDIO
S
IGNAL
P
ROCESSING
(LA71501BM)
The circuitry of Normal AUDIO part is similar to that of the conventional Normal AUDIO part in case of EE and PB
mode, but in REC mode, due to the internal opeation of self-alignment, it shows a lot of differences.
1. EE MODE
LA71501BM has 3-input VIDEO/AUDIO switching circuitry internally, and its switching is controlled by the serial data
dispatched from MICOM.
In the case of Hi-Fi models, only One input is used. The Normal AUDIO signal from Hi-Fi Audio part is divided by the
resistor, R202 and R203 and then supplied to the 73rd pin of LA71501BM. Its level is automatically controlled by ALC
and then the amplified signal through LINE AMP is obtained at the 77th pin.
The signal from C208 is supplied to REC AMP after the divider circuit (R204, R205, R207) and also to the Hi-Fi IC
BH7804K.
The ALC point can be adjusted by R208 and R209, the adjustment of which is closely related to the REC level in REC
mode.
The ALC time can be adjusted by R201 and C201.
At the MONO model, 3 input VIDEO/AUDIO switching circuit (Internal IC) is fully used. IF audio signal is supplied to
pin 71, AV signal to pin 73. Additionally F/AV signal is not used. Afterwards, Mono model is the two input system.
2. PB MODE
The PB signal picked up from AUDIO HEAD is firstly processed in the frequency characteristic compensator which is
composed of R220 and C214 (EP: C214+C215) and then supplied to the 7th pin.
The input signal passes through EQ AMP, and LINE AMP, so its output signal is finally obtained from the 77th pin.
The circuitry and its operation of EQ AMP is identical to the conventional EQ AMP.
3. REC MODE
1) AUDIO SWITCHING CIRCUIT
When the AUDIO S/W signal at the 80th pin is “H”, the point at the AUDIO HEAD of the external switching circuit is
opened electrically (EE/PB=GND), so the COIL starts to oscillated.
2) As long as the voltage difference between VCC and the 5th pn is maintained at 2.0~4.3V, the COIL oscillates. In
oher words, the COUL maintains to oscillate only if the voltage at the 5th pin is 0.7~30Vp-p.
Especially, when the R/P and FE HEAD impedance is at the center, the voltage at the 5th pin should be maintained
at 1.85Vp-p, and, if not, when the HEAD impedance is MAX or MIN, the voltage at the 5th pin is liable to deviate the
ranges of 0.7~3.0Vp-p.
The higher the FE HEAD impedance is or the lower the R/P HEAD impedance is, the higher the voltage at the 5th
pin increases.
The AC signal is put on the DC voltage at the 5th pin, and it shows the internal AUTO BIASing.
The control signal at the 6th pin controls the TR(Q205) to ON/OFF, by which the AUTO BIASing is controlled.
5
80
BIAS COIL
5th PIN
R218
REC: OPEN
EE: GND
Q203
Q204
R216
VCC
R215
Q202
R214
A-H
S/W
R217
R/P
HEAD
External Switching Circuit
Summary of Contents for DV-K*84W Series
Page 71: ...CIRCUIT DIAGRAMS 68 SECTION 9 CIRCUIT DIAGRAM 9 1 CONNECTION DIAGRAM DV K884W K484W K284W...
Page 72: ...CIRCUIT DIAGRAMS 69 9 2 POWER CIRCUIT DIAGRAM DV K884W K484W K284W...
Page 73: ...CIRCUIT DIAGRAMS 70 9 3 SYSCON AND LOGIC CIRCUIT DIAGRAM...
Page 74: ...CIRCUIT DIAGRAMS 71 9 4 PIF CIRCUIT DIAGRAM DV K884W K484W K284W...
Page 75: ...CIRCUIT DIAGRAMS 72 9 5 IF MPX MODULE CIRCUIT DIAGRAM DV K884W K484W K284W...
Page 76: ...CIRCUIT DIAGRAMS 73 9 6 VIDEO AUDIO CIRCUIT DIAGRAM DV K884W K484W K284W...
Page 77: ...CIRCUIT DIAGRAMS 74 9 7 Hi Fi PRE AMP CIRCUIT DIAGRAM DV K884W K484W K284W...
Page 78: ...DISASSEMBLY 79 SECTION 11 DISASSEMBLY 11 1 PACKING ASS Y...
